Have you made sure that both handles are engaged? There's one below the seat on your left, if your sitting in the tractor. And there's also one on the back of the tractor where you control the speed, 540 or 1000 rpm, make sure that one isn't in neutral. If neither of these fix your problem its probably going to be a clutch replacement. You may get away with just adjusting your clutch. If you need any more help feel free to give me a call.
Trevor Nystrom
Keno Tractors
Parts Department
541-850-8193
866-363-8193
Tyler Nystrom
Keno Tractors
parts@kenotractors.com
866-363-8193
Phone hours: M-F 8am to 5:30pm PST Sat 9am to 1pm PST